Set config.belongs_to_required_by_default to false
Set config.belongs_to_required_by_default to false

This will prevent validation errors when associations are not present
https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#active-record-belongs-to-required-by-default-option

alphagov/collections-publisher,alphagov/collections-publisher,alphagov/collections-publisher